From: Dave Young <dyoung@redhat.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Pingfan Liu <kernelfans@gmail.com>,
kexec@lists.infradead.org, Baoquan He <bhe@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
yinghai@kernel.org, vgoyal@redhat.com,
Randy Dunlap <rdunlap@infradead.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv7] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr
Date: Fri, 25 Jan 2019 21:45:18 +0800 [thread overview]
Message-ID: <20190125134518.GA23595@dhcp-128-65.nay.redhat.com> (raw)
In-Reply-To: <20190125103924.GB27998@zn.tnic>
> >
> > Dave Young sent the original post, and I just re-post it with commit log
>
> If he sent it, he should be the author I guess.
Just drop the line, but can change the credit to Chao Wang since he did
it initially.
But Chao does not work on kexec/kdump any more, and the email address is
outdated as well.
>
> > improvement as his requirement.
> > http://lists.infradead.org/pipermail/kexec/2017-October/019571.html
> > There was an old discussion below (previously posted by Chao Wang):
> > https://lkml.org/lkml/2013/10/15/601
>
> All that changelog info doesn't belong in the commit message ...
>
> > Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> > Cc: Dave Young <dyoung@redhat.com>
> > Cc: Baoquan He <bhe@redhat.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
> > Cc: yinghai@kernel.org,
> > Cc: vgoyal@redhat.com
> > Cc: Randy Dunlap <rdunlap@infradead.org>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: x86@kernel.org
> > Cc: linux-kernel@vger.kernel.org
> > ---
>
> .... but here.
>
> > v6 -> v7: commit log improvement
> > arch/x86/kernel/setup.c | 16 ++++++++++++++++
> > 1 file changed, 16 insertions(+)
> >
> > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> > index 3d872a5..fa62c81 100644
> > --- a/arch/x86/kernel/setup.c
> > +++ b/arch/x86/kernel/setup.c
> > @@ -551,6 +551,22 @@ static void __init reserve_crashkernel(void)
> > high ? CRASH_ADDR_HIGH_MAX
> > : CRASH_ADDR_LOW_MAX,
> > crash_size, CRASH_ALIGN);
> > +#ifdef CONFIG_X86_64
> > + /*
> > + * crashkernel=X reserve below 896M fails? Try below 4G
> > + */
> > + if (!high && !crash_base)
> > + crash_base = memblock_find_in_range(CRASH_ALIGN,
> > + (1ULL << 32),
> > + crash_size, CRASH_ALIGN);
> > + /*
> > + * crashkernel=X reserve below 4G fails? Try MAXMEM
> > + */
> > + if (!high && !crash_base)
> > + crash_base = memblock_find_in_range(CRASH_ALIGN,
> > + CRASH_ADDR_HIGH_MAX,
> > + crash_size, CRASH_ALIGN);
> > +#endif
>
> Ok, so this is silly: we know at which physical address KASLR allocated
> the kernel so why aren't we querying that and seeing if there's enough
> room before it or after it to call memblock_find_in_range() on the
> bigger range?
Baoquan may have comments?
>
> Also, why is "high" dealt with separately and why isn't the code
> enforcing "high" if the normal reservation fails?
>
AFAIK, some people prefer to explictly reserve crash memory at high
region even if it is possible to reserve at low area. May because
<4G memory is limited on large server, they want to leave this for other
use.
Yinghai or Vivek should know more about the history, probably they can
recall some initial reason.
> The presence of high is requiring from our users to pay attention what
> to use when the kernel can do all that automatically. Looks like a UI
> fail to me.
>
> And look at all the flavors of crashkernel= :
>
> crashkernel=size[KMG][@offset[KMG]]
> crashkernel=range1:size1[,range2:size2,...][@offset]
> crashkernel=size[KMG],high
> crashkernel=size[KMG],low
>
> We couldn't do one so we made 4?!?!
>
> What for?
>
> Nowhere in that help text does it explain why a user would care about
> high or low or range or offset or the planets alignment...
>
> So what's up?
Good question, still it may be some historical reason, but it is good to
make them clear and rethink about it after long time.
I also want to understand, need dig the log more.
>
> --
> Regards/Gruss,
> Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.
Thanks
Dave
next prev parent reply other threads:[~2019-01-25 13:45 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-21 5:16 [PATCHv7] x86/kdump: bugfix, make the behavior of crashkernel=X consistent with kaslr Pingfan Liu
2019-01-21 6:24 ` Baoquan He
2019-01-25 10:39 ` Borislav Petkov
2019-01-25 13:45 ` Dave Young [this message]
2019-01-25 14:08 ` Borislav Petkov
2019-01-28 9:58 ` Dave Young
2019-01-28 10:18 ` Borislav Petkov
2019-06-07 17:30 ` Borislav Petkov
2019-06-10 6:51 ` Dave Young
2019-01-29 5:25 ` Pingfan Liu
2019-01-31 7:42 ` Dave Young
2019-01-31 7:59 ` Dave Young
2019-01-31 10:57 ` Borislav Petkov
2019-01-31 22:27 ` Jerry Hoemann
2019-01-31 23:47 ` Borislav Petkov
2019-02-04 22:30 ` Jerry Hoemann
2019-02-05 8:15 ` Borislav Petkov
2019-02-06 12:08 ` Dave Young
2019-02-11 20:48 ` Dave Young
2019-02-12 5:35 ` Pingfan Liu
2019-02-15 10:24 ` Borislav Petkov
2019-02-18 1:48 ` Dave Young
2019-02-20 7:38 ` Pingfan Liu
2019-02-20 8:32 ` Borislav Petkov
2019-02-20 9:41 ` Dave Young
2019-02-20 12:51 ` Pingfan Liu
2019-02-21 17:13 ` Borislav Petkov
2019-02-22 2:11 ` Dave Young
2019-02-22 8:42 ` Joerg Roedel
2019-02-22 13:00 ` Borislav Petkov
2019-02-24 13:25 ` Pingfan Liu
2019-02-25 1:53 ` Dave Young
2019-02-25 9:39 ` Borislav Petkov
2019-02-25 11:00 ` Joerg Roedel
2019-02-25 11:12 ` Dave Young
2019-02-25 11:30 ` Borislav Petkov
2019-03-01 3:04 ` Pingfan Liu
2019-03-01 3:19 ` Pingfan Liu
2019-03-22 8:22 ` Dave Young
2019-01-29 5:51 ` Pingfan Liu
2019-01-31 10:50 ` Borislav Petkov
-- strict thread matches above, loose matches on Subject: below --
2019-01-15 8:07 Pingfan Liu
2019-01-18 3:43 ` Dave Young
2019-01-19 1:25 ` Jerry Hoemann
2019-01-21 5:11 ` Pingfan Liu
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